A cold and influenza are diseases mainly caused by infection with a virus and resulting in poor physical conditions. Experiencing the outbreak of the new influenza, people are seeking for beverages and foods having the immunopotentiating effect for preventing a cold and influenza. Lactic acid strains such as Lactococcus lactis subsp. lactis JCM5805 (see Patent Literature 1), Lactbacillus bulgaricus OLL1073R-1 (see Patent Literature 2), Enterococcus faecalis (see Patent Literature 3), Lactobacillus brevis subsp. coagulans (see Patent Literature 4), and Lactococcus gasseri (see Patent Literature 5) have been known to exhibit the immunopotentiating effect and used in plural beverages and foods. However, to have an adequate effect of such bacteria, an amount of the bacteria exceeding a certain amount has been required and addition of a large amount of such bacteria in a beverage has resulted in decrease in the commercial value due to, for example, production of precipitates and/or flavor deterioration. Therefore, a method for having an adequate effect of such lactic acid bacteria in a small quantity has been desired. Methods for increasing the immunopotentiating effect of lactic acid bacteria and products having an enhanced immunological effect have been reported recently. Examples include beverages and foods for increasing immunity, comprising a combination of lactic acid bacteria and cereals of a Poaceae plant (see Patent Literature 5); a composition comprising fucoidan or a fucoidan hydrolysate and an immuno-stimulating material (see Patent Literature 6); a culture obtained by lactic fermentation involving inoculating a medium containing a processed asparagus product with lactic acid bacteria (see Patent Literature 7); a method involving combined use of lactic acid bacteria and ascorbic acid (see Patent Literature 8); and a method involving combined use of lactic acid bacteria and vitamin E (see Patent Literature 9).